Production of renewable liquid fuels directly from biomass resources is of great importance in view of the present high consumption of fossil fuels. Today, about three quarters of the world's energy is provided by fossil fuels such as coal, oil, and natural gas. Fossil fuels, however, are nonrenewable resources. Diminishing reserves of fossil fuels and growing concerns about global warming call for sustainable sources of energy such as renewable liquid fuels.
The increasing cost of fossil fuels and the concerns about their environmental impact are accelerating the transition to a biomass-based economy. While fuel production from biomass has gained significant attention, the use of renewable resources in the production of chemicals is also very important. Typically, chemical intermediates have much greater utility than fuels since they may be transformed into solvents, polymers, and specialty chemicals for which fossil fuels have traditionally been used.
A known method for producing liquid fuels from biomass entails fermentation of sugars to produce ethanol. Ethanol, however, is not a good candidate for a liquid fuel due to its low energy density (23 MJ/L), high volatility (BP 78° C.), and high solubility in water (fully miscible). Liquid fuel candidates such as 2,5-dimethylfuran (DMF) and 2,5-dimethyltetrahydrofuran (DMTHF) which can be produced from renewable biomass therefore have gained interest.
It is known to use a two-step synthesis of 2,5-dimethylfuran (DMF) via 5-hydroxymethylfurfural (HMF) produced by dehydration of fructose. However, the application of this two-step synthesis is limited due to low yield and complicated separations. Moreover, a typical method for manufacture of HMF from cellulose entails either use of aqueous acid hydrolysis at high temperatures and pressures (250-400° C., 10 MPa) at less than 30% yield or use of expensive ionic liquid as solvent.
5-methylfurfural is a useful intermediate for production of pharmaceuticals, agriculture chemicals, perfumes and the like. Large-scale production of 5-methylfurfural employs 5-methylfuran, N,N dimethylformamide and phosphorus oxychloride or phosgene. During manufacture of 5-methylfurfural, a significant excess of poisonous phosphorus oxychloride and N,N-dimethylformamide are used.
Although methods for manufacture of biomass derived liquid fuels are known, these methods have numerous disadvantages as discussed above. A need therefore exists for a method of generating renewable liquid fuels that addresses the disadvantages of the prior art.